Big animals, big poop and big problems for Earth

The vast reduction in large animal species is having a dreadful impact on the planet, with less big animal poop meaning less circulation of crucial nutrients throughout the planet.

A new study has looked at how giant whales play a huge part in disseminating vast quantities of phosphorous throughout our oceans and large land-based animals bring nutrients to various locations in a type of natural, organic, self-sustaining ecosystem.

With the end of the last ice age, most megafauna went extinct, cutting off the land-locked supply chain, with modern sea hunting all but eliminating the capabilities of whales.

Add to that the reduction in major bird populations that could previously have been relied on to bring phosphorous from the sea back into land and there’s three supply lines cut off.

So now our rivers aren’t getting the sea-based nutrients they previously relied on, and parts of the planet’s foliage has receded due to reduced circulation – via the digestive system – of migrating animals.

Broken cycle in the environment

“This broken global cycle may weaken ecosystem health, fisheries, and agriculture,” said Joe Roman, co-author on the new study.

The capacity of modern animals to carry nutrients away from what Roman calls “hotspots” and into underpopulated areas has reduced to 8pc of what it was before the ice age.

“Previously, animals were not thought to play an important role in nutrient movement,” said lead author Christopher Doughty, but the latest piece of research claims large animals in particular are a “distribution pump”.

They essentially transport large amounts of fecal matter to fertilise many places that would otherwise be less productive, including ocean surface waters and the interior of continents.

Think of them as the labour needed to transport things that the wind just can’t carry.

The planet needs to be fertilised

By fertilising ecosystems that cannot sustain themselves, the animals maintain natural functions vital to people. For example, the new study notes that restoring whale populations could help increase the ocean’s capacity to absorb climate-warming carbon dioxide.

The scientists focused mostly on phosphorous, a nutrient critical for plant growth.

Prior to the era of commercial hunting, the scientists estimate that whales and other marine mammals annually moved around 750 million pounds of phosphorus from the depths to the surface. It’s less than a quarter of that now.

The reduction in the Blue Whale population, from 350,000 down to just a few thousand today, is playing a major role in this.

This diagram shows an interlinked system of animals that carry nutrients from ocean depths to deep inland – through their poop, urine, and, upon death, decomposing bodies, via PNAS journal.

Changes from top to bottom

“This study challenges the bottom-up bias that some scientists have – that microbes are running the show, and phytoplankton and plants are all that matter,” said Roman.

The planet’s whale, fish, seabird and large herbivore population has plummeted many times over from its peak levels, with the likes of giant deer or elephant-like gomphotheres and bison populations of epic proportions now gone, which has greatly harmed the cycle of moving nutrients upstream, an area not previously investigated to a huge degree.

“The typical flow of nutrients is down mountains to the oceans,” said Roman.

“We are looking at ways that nutrients can go in the other direction – and that’s largely through foraging animals. They’re bringing nutrients from the deep sea that could eventually reach a mountain in British Columbia.”